Long Term Evolution (Long Term Evolution, LTE for short) is a standard of the 3rd Generation Partnership Project (3rd Generation Partnership Project, 3GPP for short), and is considered as a mainstream technology for evolution from a third generation mobile telecommunications technology (3rd-generation, 3G for short) to a fourth generation mobile telecommunications technology (4th-generation, 4G for short). The LTE includes frequency division duplex (Frequency Division Duplexing, FDD for short) and time division duplex (Time Division Duplexing, TDD for short). In an LTE-TDD system, a same frequency band is used on an uplink and a downlink, and the uplink is distinguished from the downlink merely depending on time.
In the LTE-TDD system, an existing data transmission method includes: determining, by an evolved NodeB (evolved Node B, eNB for short), a downlink modulation and coding scheme (Modulation and Coding Scheme, MCS for short) of user equipment (User Equipment, UE for short) according to a downlink channel quality indicator (Channel Quality Indicator, CQI for short) fed back by the UE; and allocating a transmission resource according to the downlink MCS of the UE. The UE generally assumes that a downlink transmission mode is a transmit diversity mode or a closed-loop spatial multiplexing mode, and determines a downlink CQI according to the assumed downlink transmission mode.
During implementation of the present invention, it is found that the prior art has at least the following problem:
When the eNB transmits downlink data by using a beamforming (Beamforming, BF for short) mode, the downlink transmission mode assumed by the UE is the transmit diversity mode or the closed-loop spatial multiplexing mode, and this is different from a transmission mode actually used by the eNB. Because the CQI is determined according to the downlink transmission mode assumed by the UE, the CQI determined by the UE may be inaccurate; consequently, the downlink MCS determined by the eNB according to the CQI fed back by the UE is inaccurate. In addition, the CQI obtained by the eNB is a quantized value (obtained by the UE through calculation), and a quantization error exists, which may lead to inaccuracy of the downlink MCS determined by the eNB. The inaccurate downlink MCS affects transmission efficiency, and causes some losses of system performance.